The NF-?B/Rel family of transcription factors contributes to critical cellular processes, including immune, inflammatory and cell survival responses. As such, NF-?B is implicated in immunity-related diseases, such as autoimmunity, as well as multiple types of human malignancies. Understanding mechanisms of NF-?B regulation will not only expand our knowledge of basic cell signaling processes but also provide potential avenues to prevent and/or treat these human disorders. While a large body of literature over the last two decades describes the critical roles of ubiquitin in regulating NF-?B functions, very little is known about regulation of NF-?B signaling by SUMO (small ubiquitin-like modifier), another posttranslational modifier. The long-term goal of this project is to greatly expand our understanding of the mechanisms of NF-?B and SUMO regulation in specific physiological and pathological processes. We have recently uncovered a novel signaling role for SUMOylation of NEMO (NF-?B essential modulator) in NF-?B signaling. Our preliminary data indicate that there exist significant, novel crosstalk mechanisms between the SUMO and NF-?B pathways. Thus, in this proposal, we will test the hypothesis that crosstalk between SUMO and NF-?B signaling systems plays critical roles in regulating certain physiological and pathological processes. This research is expected to considerably expand our knowledge of the molecular links between SUMO and NF-?B pathways and their roles in specific physiological and pathological processes. This research will also generate novel reagents and tools to allow other researchers to investigate SUMO and NF-?B signaling systems in similar and different experimental models. Finally, it may also identify rational targets for drug development against human disorders, such as autoimmunity and specific types of malignancies. PUBLIC HEALTH RELEVANCE: The regulation of cancer cell death is a complex process involving many different molecular pathways. This research seeks to understand the relationships between protein modification by SUMO (Small Ubiquitin-like Modifier) and NF-?B signaling, one of the major cell death-regulatory pathways. This study will significantly expand our understanding of the regulatory mechanisms for normal and cancer cell death signaling, and may also provide rationale targets for the development of new anticancer drugs.